Many of general ophthalmic solutions contain terpenoids such as menthol, camphor, borneol and the like as algefacients in order to provide a cool sensation and a refreshing feel upon instillation. While plastic containers are generally used for such ophthalmic solutions, the terpenoid content is known to decrease when a drug containing terpenoid is filled and preserved in a plastic container. To solve this problem, JP-A-2000-273061 discloses an oil-in-water emulsion ophthalmic solution in a plastic container wherein decrease in the terpenoid content is suppressed. Moreover, JP-A-2002-003364 discloses a method of suppressing adsorption of algefacients such as menthol and the like to a container, which comprises adding polyvalent alcohol into a unit-dose (disposable) eyedrop container.
Lacrimal fluid is known to have pseudoplasticity. That is, the viscosity of lacrimal fluid decreases when a force is applied by blinking, and increases when the force is not applied. Therefore, lacrimal fluid has unique property in that it has low viscosity and becomes thin during blinking to facilitate blinking, but it becomes highly viscose before and after blinking to cover the eye surface for protection. As a polymer compound showing such pseudoplasticity, xanthan gum is known.
As an ophthalmic composition containing xanthan gum, the following have been reported. For example, an ophthalmic composition containing echothiopate iodide and xanthan gum is disclosed, and xanthan gum has been reported to enhance the treatment effect of echothiopate iodide (U.S. Pat. No. 4,136,177). In addition, an ophthalmic composition containing xanthan gum and a carbonic anhydrase inhibitor has been disclosed, where xanthan gum is used to improve ophthalmic bioavailability of the carbonic anhydrase inhibitor (JP-T-2001-508035, JP-T-2002-501017, JP-T-2002-506461). For the purpose of improving ophthalmic bioavailability of a drug, xanthan gum is used, and an ophthalmic composition containing a carbonic anhydrase inhibitor, a prostaglandin derivative and xanthan gum has been disclosed (JP-T-2002-501533, JP-T-2002-521332, JP-T-2002-521333). An ophthalmic composition containing quaternary nitrogen-containing ethoxylated glycoside and xanthan gum has been disclosed for the treatment of dry eye (JP-T-2001-516713). In addition, an ophthalmic composition containing xanthan gum, which is gelated upon contact with the eye, has been disclosed (JP-T-2002-510654). Moreover, U.S. Pat. No. 6,623,751 reports in connection with skin patches that can be adapted to the shape of around the eye, forehead, nose, the mouth and the like, a patch containing a hydrophilic gelling system in an aqueous phase. Example 3 of U.S. Pat. No. 6,623,751 reports a patch containing xanthan gum and menthol.
However, there has been no report on an ophthalmic solution comprising xanthan gum and terpenoid. Moreover, suppression of decrease in the terpenoid content by xanthan gum in an ophthalmic solution has not been reported.